* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Resistance is the opposition that a substance offers to the flow of
History of electromagnetic theory wikipedia , lookup
Voltage optimisation wikipedia , lookup
Three-phase electric power wikipedia , lookup
Electric power system wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Mains electricity wikipedia , lookup
Electric motor wikipedia , lookup
Wireless power transfer wikipedia , lookup
Amtrak's 25 Hz traction power system wikipedia , lookup
Brushed DC electric motor wikipedia , lookup
Distributed generation wikipedia , lookup
Life-cycle greenhouse-gas emissions of energy sources wikipedia , lookup
Transformer types wikipedia , lookup
Transformer wikipedia , lookup
Variable-frequency drive wikipedia , lookup
History of electric power transmission wikipedia , lookup
Stepper motor wikipedia , lookup
Resonant inductive coupling wikipedia , lookup
Alternating current wikipedia , lookup
Power engineering wikipedia , lookup
Electric machine wikipedia , lookup
Resistance is the opposition that a substance offers to the flow of electric current. It is represented by the uppercase letter R. The standard unit of resistance is the ohm, sometimes written out as a word, and sometimes symbolized by the uppercase Greek letter omega: When an electric current of one ampere passes through a component across which a potential difference (voltage) of one volt exists, then the resistance of that component is one ohm. (For more discussion of the relationship among current, resistance and voltage, see Ohm's law.) In general, when the applied voltage is held constant, the current in a direct-current (DC) electrical circuit is inversely proportional to the resistance. If the resistance is doubled, the current is cut in half; if the resistance is halved, the current is doubled. This rule also holds true for most low-frequency alternating-current (AC) systems, such as household utility circuits. In some AC circuits, especially at high frequencies, the situation is more complex because some components in these systems can store and release energy, as well as dissipating or converting it. The electrical resistance per unit length, area, or volume of a substance is known as resistivity. Resistivity figures are often specified for copper and aluminum wire, in ohms per kilometer. Opposition to AC, but not to DC, is a property known as reactance. In an AC circuit, the resistance and reactance combine vectorially to yield impedance. Resistance contrasts with conductance, which is a measure of the ease with which electrical current flows through a substance. What is transformer? Definition & Working Principle of Transformer Definition of Transformer Electrical power transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of mutual induction between two windings. It transforms power from one circuit to another without changing its frequency but may be in different voltage level. This is a very short and simple definition of transformer, as we will go through this portion of tutorial related to electrical power transformer, we will understand more clearly and deeply "what is transformer ?" and basic theory of transformer. Working Principle of Transformer The working principle of transformer is very simple. It depends upon Faraday's law of electromagnetic induction. Actually, mutual induction between two or more winding is responsible for transformation action in an electrical transformer. Faraday's Laws of Electromagnetic Induction According to these Faraday's laws, "Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil". Basic Theory of Transformer Say you have one winding which is supplied by an alternating electrical source. The alternating current through the winding produces a continually changing flux or alternating flux that surrounds the winding. If any other winding is brought nearer to the previous one, obviously some portion of this flux will link with the second. As this flux is continually changing in its amplitude and direction, there must be a change in flux linkage in the second winding or coil. According to Faraday's law of electromagnetic induction, there must be an EMF induced in the second. If the circuit of the later winding is closed, there must be an current flowing through it. This is the simplest form of electrical power transformer and this is the most basic of working principle of transformer. For better understanding, we are trying to repeat the above explanation in a more brief way here. Whenever we apply alternating current to an electric coil, there will be an alternating flux surrounding that coil. Now if we bring another coil near the first one, there will be an alternating flux linkage with that second coil. As the flux is alternating, there will be obviously a rate of change in flux linkage with respect to time in the second coil. Naturally emf will be induced in it as per Faraday's law of electromagnetic induction. This is the most basic concept of the theory of transformer. The winding which takes electrical power from the source, is generally known as primary winding of transformer. Here in our above example it is first winding. The winding which gives the desired output voltage due to mutual induction in the transformer, is commonly known as secondary winding of transformer. Here in our example it is second winding. The above mentioned form of transformer is theoretically possible but not practically, because in open air very tiny portion of the flux of the first winding will link with second; so the current that flows through the closed circuit of later, will be so small in amount that it will be difficult to measure. The rate of change of flux linkage depends upon the amount of linked flux with the second winding. So, it is desired to be linked to almost all flux of primary winding to the secondary winding. This is effectively and efficiently done by placing one low reluctance path common to both of the winding. This low reluctance path is core of transformer, through which maximum number of flux produced by the primary is passed through and linked with the secondary winding. This is the most basic theory of transformer. Main Constructional Parts of Transformer The three main parts of a transformer are, 1. Primary Winding of transformer - which produces magnetic flux when it is connected to electrical source. 2. Magnetic Core of transformer - the magnetic flux produced by the primary winding, that will pass through this low reluctance path linked with secondary winding and create a closed magnetic circuit. 3. Secondary Winding of transformer - the flux, produced by primary winding, passes through the core, will link with the secondary winding. This winding also wounds on the same core and gives the desired output of the transformer. Power Plants & Types of Power Plant Under Electrical Power Generation What is Power Plant? Types of Power Station • Thermal • Nuclear • Hydro-Electric Types of Power Generation What is Power Plant? A power plant or a power generating station, is basically an industrial location that is utilized for the generation and distribution of electric power in mass scale, usually in the order of several 1000 Watts. These are generally located at the sub-urban regions or several kilometers away from the cities or the load centers, because of its requisites like huge land and water demand, along with several operating constraints like the waste disposal etc. For this reason, a power generating station has to not only take care of efficient generation but also the fact that the power is transmitted efficiently over the entire distance. And that’s why, the transformer switch yard to regulate transmission voltage also becomes an integral part of the power plant. At the center of it, however, nearly all power generating stations has an A.C. generator or an alternator, which is basically a rotating machine that is equipped to convert energy from the mechanical domain (rotating turbine) into electrical domain by creating relative motion between a magnetic field and the conductors. The energy source harnessed to turn the generator shaft varies widely, and is chiefly dependent on the type of fuel used. Types of Power Station A power plant can be of several types depending mainly on the type of fuel used. Since for the purpose of bulk power generation, only thermal, nuclear and hydro power comes handy, therefore a power generating station can be broadly classified in the 3 above mentioned types. Let us have a look in these types of power stations in details. Thermal Power Station A thermal power station or a coal fired thermal power plant is by far, the most conventional method of generating electric power with reasonably high efficiency. It uses coal as the primary fuel to boil the water available to superheated steam for driving the steam turbine. The steam turbine is then mechanically coupled to an alternator rotor, the rotation of which results in the generation of electric power. Generally in India, bituminous coal or brown coal are used as fuel of boiler which has volatile content ranging from 8 to 33 % and ash content 5 to 16 %. To enhance the thermal efficiency of the plant, the coal is used in the boiler in its pulverized form. In coal fired thermal power plant, steam is obtained in very high pressure inside the steam boiler by burning the pulverized coal. This steam is then super heated in the super heater to extreme high temperature. This super heated steam is then allowed to enter into the turbine, as the turbine blades are rotated by the pressure of the steam. The turbine is mechanically coupled with alternator in a way that its rotor will rotate with the rotation of turbine blades. After entering into the turbine, the steam pressure suddenly falls leading to corresponding increase in the steam volume. After having imparted energy into the turbine rotors, the steam is made to pass out of the turbine blades into the steam condenser of turbine. In the condenser, cold water at ambient temperature is circulated with the help of pump which leads to the condensation of the low pressure wet steam. Then this condensed water is further supplied to low pressure water heater where the low pressure steam increases the temperature of this feed water, it is again heated in high pressure. This outlines the basic working methodology of a thermal power plant. Nuclear Power Station The nuclear power generating stations are similar to the thermal stations in more ways than one. How ever, the exception here is that, radioactive elements like Uranium and thorium are used as the primary fuel in place of coal. Also in a Nuclear station the furnace and the boiler are replaced by the nuclear reactor and the heat exchanger tubes. For the process of nuclear power generation, the radioactive fuels are made to undergo fission reaction within the nuclear reactors. The fission reaction, propagates like a controlled chain reaction and is accompanied by unprecedented amount of energy produced, which is manifested in the form of heat. This heat is then transferred to the water present in the heat exchanger tubes. As a result, super heated steam at very high temperature is produced. Once the process of steam formation is accomplished, the remaining process is exactly similar to a thermal power plant, as this steam will further drive the turbine blades to generate electricity. Hydro-Electric Power Station In Hydro-electric plants the energy of the falling water is utilized to drive the turbine which in turn runs the generator to produce electricity. Rain falling upon the earth’s surface has potential energy relative to the oceans towards which it flows. This energy is converted to shaft work where the water falls through an appreciable vertical distance. The hydraulic power is therefore a naturally available renewable energy given by the eqn: P =gρ QH Where g = acceleration due to gravity = 9.81 m/sec 2 ρ = density of water = 1000 kg/m 3 H = height of fall of water. This power is utilized for rotating the alternator shaft, to convert it to equivalent electrical energy. An important point to be noted is that, the hydro-electric plants are of much lower capacity compared to their thermal or nuclear counterpart. For this reason hydro plants are generally used in scheduling with thermal stations, to serve the load during peak hours. They in a way assist the thermal or the nuclear plant to deliver power efficiently during periods of peak hours. Types of Power Generation As mentioned above, depending on the type of fuel used, the power generating stations as well as the types of power generation are classified. Therefore the 3 major classifications for power production in reasonably large scale are :1) Thermal power generation. 2) Nuclear power generation. 3) Hydro-electric power generation. Apart from these major types of power generations, we can resort to small scale generation techniques as well, to serve the discrete demands. These are often referred to as the alternative methods of power generation and can be classified as :1) Solar power generation. (making use of the available solar energy) 2) Geo-thermal power generation. (Energy available in the Earth’s crust) 3) Tidal power generation. These alternative sources of generation has been given due importance in the last few decades owing to the depleting amount of the natural fuels available to us. In the centuries to come, a stage might be reached when several countries across the globe would run out of their entire reserve for fossil fuels. The only way forward would then lie in the mercy of these alternative sources of energy which might play an instrumental role in shaping the energy supplies of the future. For this reason these might rightfully be referred as the energy of the future. Alternator Synchronous Generator | Definition and Types of Alternator Under Electrical Generator Definition of Alternator • History • Application • Types Definition of Alternator The definition of alternator is hidden in the name of this machine itself. An alternator is such a machine which produces alternation electricity. It is a kind of generators which converts mechanical energy into alternating electrical energy. It is also known as synchronous generator. History of Alternator Michael Faraday and Hippolyte Pixii gave the very first concept of alternator. Michael Faraday designed a rotating rectangular turn of conductor inside a magnetic field to produce alternating current in the external static circuit. After that in the year of 1886 J.E.H. Gordon, designed and produced first prototype of useful model. After that Lord Kelvin and Sebastian Ferranti designed a model of 100 to 300 Hz synchronous generator. Nikola Tesla in 1891, designed a commercially useful 15 KHz generator. After this year, poly phase alternators were come into picture which can deliver currents of multiple phases. Use of Alternator The power for electrical system of modern vehicles produces from alternator. In previous days, DC generators or dynamos were used for this purpose but after development of alternator, the dc dynamos are replaced by more robust and light weight alternator. Although the electrical system of motor vehicles generally requires direct current but still an alternator along with diode rectifier instead of a DC generator is better choice as the complicated commutation is absent here. This special type of generator which is used in vehicle is known as automotive alternator. Another use of alternator is in diesel electric locomotive. Actually the engine of this locomotive is nothing but an alternator driven by diesel engine. The alternating current produced by this generator is converted to DC by integrated silicon diode rectifiers to feed all the dc traction motors. And these dc traction motors drive the wheel of the locomotive. This machine is also used in marine similar to diesel electric locomotive. The synchronous generator used in marine is specially designed with appropriate adaptations to the salt-water environment. The typical output level of marine alternator is about 12 or 24 volt. In large marine, more than one units are used to provide large power. In this marine system the power produced by alternator is first rectified then used for charging the engine starter battery and auxiliary supply battery of marine. Types of Alternator Alternators or synchronous generators can be classified in may ways depending upon their application and design. According to application these machines are classified as1. 2. 3. 4. 5. Automotive type - used in modern automobile. Diesel electric locomotive type - used in diesel electric multiple unit. Marine type - used in marine. Brush less type - used in electrical power generation plant as main source of power. Radio alternators - used for low brand radio frequency transmission. These ac generators can be divided in many ways but we will discuss now two main types of alternator categorized according to their design. These are1. Salient pole type It is used as low and medium speed alternator. It has a large number of projecting poles having their cores bolted or dovetailed onto a heavy magnetic wheel of cast iron or steel of good magnetic quality. Such generators are characterized by their large diameters and short axial lengths. These generator are look like big wheel. These are mainly used for low speed turbine such as in hydral power plant. 2. Smooth cylindrical type It is used for steam turbine driven alternator. The rotor of this generator rotates in very high speed. The rotor consists of a smooth solid forged steel cylinder having a number of slots milled out at intervals along the outer periphery for accommodation of field coils. These rotors are designed mostly for 2 pole or 4 pole turbo generator running at 36000 rpm or 1800 rpm respectively. 3.Electrical Motor | Types Classification and History of Motor Under Electrical Motor Electrical Motor Classification or Types of Motor History of Motor 4. Electrical Motor The motor or an electrical motor is a device that has brought about one of the biggest advancements in the fields of engineering and technology ever since the invention of electricity. A motor is nothing but an electro-mechanical device that converts electrical energy to mechanical energy. Its because of motors, life is what it is today in the 21st century. Without motor we had still been living in Sir Thomas Edison’s Era where the only purpose of electricity would have been to glow bulbs. There are different types of motor have been developed for different specific purposes. In simple words we can say a device that produces rotational force is a motor. The very basic principal of functioning of an electrical motor lies on the fact that force is experienced in the direction perpendicular to magnetic field and the current, when field and current are made to interact with each other. Ever since the invention of motors, a lot of advancements has taken place in this field of engineering and it has become a subject of extreme importance for modern engineers. This particular webpage takes into consideration, the above mentioned fact and provides a detailed description on all major electrical motors and motoring parts being used in the present era. 5. Classification or Types of Motor The primary classification of motor or types of motor can be tabulated as shown, 6. History of Motor In the year 1821 British scientist Michael Faraday explained the conversion of electrical energy into mechanical energy by placing a current carrying conductor in a magnetic field which resulted in the rotation of the conductor due to torque produced by the mutual action of electrical current and field. Based on his principal the most primitive of machines a D.C.(direct current) machine was designed by another British scientist William Sturgeon in the year 1832. But his model was overly expensive and wasn’t used for any practical purpose. Later in the year 1886 the first electrical motor was invented by scientist Frank Julian Sprague. That was capable of rotating at a constant speed under a varied range of load, and thus derived motoring action. INDEX DC Motor Synchronous Motor 3 Phase Induction Motor 1 Phase Induction Motor Special Types of Motor Among the four basic classification of motors mentioned above the DC motor as the name suggests, is the only one that is driven by direct current. It’s the most primitive version of the electric motor where rotating torque is produced due to flow of current through the conductor inside a magnetic field. Rest all are A.C. electrical motors, and are driven by alternating current, for e.g. the synchronous motor, which always runs at synchronous speed. Here the rotor is an electro - magnet which is magnetically locked with stator rotating magnetic field and rotates with it. The speed of these machines are varied by varying the frequency (f) and number of poles (P), as Ns = 120 f/P. In another type of AC motor where rotating magnetic field cuts the rotor conductors, hence circulating current induced in these short circuited rotor conductors. Due to interaction of the magnetic field and these circulating currents the rotor starts rotates and continues its rotation. This is induction motor which is also known as asynchronous motor runs at a speed lesser than synchronous speed, and the rotating torque, and speed is governed by varying the slip which gives the difference between synchronous speed Ns , and rotor speed speed Nr, It runs governing the principal of EMF induction due to varying flux density, hence the name induction machine comes. Single phase induction motor like a 3 phase, runs by the principal of emf induction due to flux, but the only difference is, it runs on single phase supply and its starting methods are governed by two well established theories, namely the Double Revolving field theory and the Cross field theory. Apart from the four basic types of motor mentioned above, there are several types Of special electrical motors like Linear Induction motor(LIM),Stepper motor, Servo motor etc with special features that has been developed according to the needs of the industry or for a particular gadget like the use of hysteresis motor in hand watches because of its compactness.